Wafer plate and mask arrangement for substrate fabrication

ABSTRACT

A system for processing wafers in a vacuum processing chamber. Carrier comprising a frame having a plurality of openings, each opening configured to accommodate one wafer. A transport mechanism configured to transport the plurality of carriers throughout the system. A plurality of wafer plates configured for supporting wafers. An attachment mechanism for attaching a plurality of wafer plates to each of the carriers, wherein each of the wafer plates is attached to a corresponding position at an underside of a corresponding carrier, such that each of the wafers positioned on one of the wafer carriers is positioned within one of the plurality of opening in the carrier. Mask attached over front side of one of the plurality of opening in the carrier. Alignment stage supports wafer plate under the opening in the carrier. A camera positioned to simultaneously image the mask and the wafer.

RELATED APPLICATIONS

This application claims priority benefit from U.S. ProvisionalApplication No. 62/235,898, filed Oct. 1, 2015. This application is alsoa continuation-in-part of U.S. patent application Ser. No. 13/866,856,filed Apr. 19, 2013, and which claims priority benefit from U.S.Provisional Application No. 61/639,052, filed Apr. 26, 2012 and U.S.Provisional Application No. 61/635,804, filed Apr. 19, 2012. Thisapplication is also a continuation-in-part of U.S. patent applicationSer. No. 13/871,871, filed Apr. 26, 2013, and which claims prioritybenefit from U.S. Provisional Application No. 61/639,052, filed Apr. 26,2012. The entire disclosures of which are incorporated herein byreference.

BACKGROUND 1. Field

This application relates to systems for vacuum processing, such assystems used in the fabrication of solar cells, flat panel displays,touch screens, etc.

2. Related Art

Various systems are known in the art for fabricating semiconductor IC's,solar cells, touch screens, etc. The processes of these systems areconducted in vacuum and include, e.g., physical vapor deposition (PVD),chemical vapor deposition (CVD), ion implant, etch, etc. There are twobasic approaches for such systems: single-substrate processing or batchprocessing. In single wafer processing, only a single substrate ispresent inside the chamber during processing. In batch processingseveral substrates are present inside the chamber during processing.Single substrate processing enables high level of control of the processinside the chamber and the resulting film or structure fabricated on thesubstrate, but results in a relatively low throughput. Conversely, batchprocessing results in less control over the processing conditions andthe resulting film or structure, but provides a much higher throughput.

Batch processing, such as that employed in systems for fabricating solarcells, touch panels, etc., is generally performed by transporting andfabricating the substrates in a two-dimensional array of n×m substrates.For example, a PECVD system for solar fabrication developed by Roth &Rau utilizes trays of 5×5 wafers for a reported 1200 wafers/hourthroughput in 2005. However, other systems utilize trays having twodimensional arrays of 6×6, 7×7, 8×8, and even higher number of wafers.While throughput is increased utilizing trays of two-dimensional waferarrays, the handling and the loading and unloading operations of suchlarge trays becomes complex.

In some processes, it is required to apply bias, e.g., RF or DCpotential, to the substrate being processed. However, since batch systemutilize a moving tray with the substrates, it is difficult to apply thebias.

Also, while some processes can be performed with the substrate heldhorizontally, some processes can benefit from a vertically heldsubstrate. However, loading and unloading of substrate vertically iscomplex compared to horizontal loading and unloading.

Some processes may require the use of masks to block parts of thesubstrate from the particular fabrication process. For example, masksmay be used for formation of contacts or for edge exclusion to preventshunting of the cell. That is, for cells having contacts on the frontand back sides, materials used for making the contacts may be depositedon the edges of the wafer and shunt the front and back contacts.Therefore, it is advisable to use mask to exclude the edges of the cellduring fabrication of at least the front or back contacts.

As another illustration, for the fabrication of silicon solar cells, itis desirable to deposit blanket metals on the back surface to act aslight reflectors and electrical conductors. The metal is typicallyaluminum, but the blanket metals could be any metal used for multiplereasons, such as cost, conductivity, solderability, etc. The depositedfilm thickness may be very thin, e.g., about 10 nm up to very thick,e.g., 2-3 um. However, it is necessary to prevent the blanket metal fromwrapping around the edge of the silicon wafer, as this will create aresistive connection between the front and back surfaces of the solarcell, i.e., shunting. To prevent this connection, an exclusion zone onthe backside edge of the wafer can be created. The typical dimension ofthe exclusion zone is less than 2 mm wide, but it is preferable to makethe exclusion as thin as possible.

One way to create this exclusion zone is through the use of a mask;however, using masks has many challenges. Due to the highly competitivenature of the solar industry, the mask must be very cheap tomanufacture. Also, due to the high throughputs of solar fabricationequipment (typically 1500-2500 cells per hour), the mask must be quickand easy to use in high volume manufacturing. Also, since the mask isused to prevent film deposition on certain parts of the wafer, it mustbe able to absorb and accommodate deposition build up. Furthermore,since film deposition is done at elevated temperatures, the mask must beable to function properly at elevated temperature, e.g., up to 350° C.,while still accurately maintaining the exclusion zone width, whileaccommodating substrate warpage due to thermal stresses.

SUMMARY

The following summary is included in order to provide a basicunderstanding of some aspects and features of the invention. Thissummary is not an extensive overview of the invention and as such it isnot intended to particularly identify key or critical elements of theinvention or to delineate the scope of the invention. Its sole purposeis to present some concepts of the invention in a simplified form as aprelude to the more detailed description that is presented below.

Embodiments of the invention provide a system architecture that ismodular, in that it enables using different processes and process steps,and versatile, in that it is suitable for fabrication of variousdevices, including, e.g., solar cells, flat panel displays, touchscreens, etc. Moreover, the system can handle different types and sizesof substrates without reconfiguration, but by simply changing thesusceptors used.

The system architecture enables substrate handling, such as loading andunloading in atmospheric environment, separate from the vacuumprocessing. Additionally, various embodiments enable manual loading andunloading with automation in idle or not present, i.e., the system canbe implemented without loading/unloading automation. Inside the vacuumenvironment the system enables static or pass-by processing of thesubstrates. In certain embodiments, vacuum isolation is provided betweeneach processing chamber, using actuated valves. Various embodimentsprovide for electrostatic chucking of the substrates to enable efficientcooling and to prevent accidental movement of the substrates. In otherembodiments, mechanical chucking is enabled using, e.g., spring-loadedclips with relief mechanism for loading/unloading of the substrates.Various embodiments also enable biasing of the substrates using, e.g.,RF or DC bias power, or floating the substrate.

Various embodiments enable simplified handling of substrates by havingthe handling performed on line-array carriers, while processing isperformed on a two-dimensional array of n×m substrates, by processingseveral line-array carriers simultaneously. Other embodiments providefor transport mechanism wherein the substrates are processed in avertical orientation, but loading and unloading is performed while thesubstrates are handled horizontally.

Embodiments of the invention also enable substrate processing usingmasks, which can be implemented by using a dual-mask arrangement. Thetwo part masking system is configured for masking substrates, andincludes an inner mask consisting of a flat metal sheet having aperturesexposing the parts of the wafer that are to be processed; and, an outermask configured for placing over and masking the inner mask, the outermask having an opening cut of size and shape similar to the size andshape of the substrate, the outer mask having thickness larger thanthickness of the inner mask. A mask frame may be configured to supportthe inner and outer masks, such that the outer mask is sandwichedbetween the mask frame and the inner mask. In one example, where thedual-mask arrangement is used for edge isolation, the opening cut in theinner mask is of size slightly smaller than the solar wafer, so thatwhen the inner mask is placed on the wafer it covers peripheral edge ofthe wafer, and the opening cut in the outer mask is slightly larger thanthe opening cut in of the inner mask. A top frame carrier may be used tohold the inner and outer mask and affix the inner and outer masks to thewafer susceptor.

A loading and unloading mechanism is provided, which handles four rowsof substrates simultaneously. The loading/unloading mechanism isconfigured for vertical motion, having a lowered position and anelevated position. In its lowered position, the mechanism is configuredto simultaneously: remove a row of processed substrates from onecarrier, deposit a row of fresh substrates on an empty carrier, deposita row of processed substrates on a substrate removal mechanism, andcollect a row of fresh substrates from a substrates delivery mechanism.The substrate removal mechanism and the substrate delivery mechanism maybe conveyor belts moving in the same or opposite directions. In itselevated position, the mechanism is configured to rotate 180 degrees.

In certain embodiments, an arrangement is utilized wherein wafer platesare attached to carriers from the underside, while the mask arrangementis attached to the carrier from above. One of the wafer plate or maskarrangement is attached to the carrier in a fixed orientation, while theother may be realigned upon loading of each new wafer. In illustrativeembodiments, the mask arrangement is placed on the carrier in a fixedorientation. Once a new wafer is loaded onto a wafer plate, the waferplate is brought to its position under the carrier. A camera is thenused to verify the alignment of the wafer with respect to the maskarrangement. The wafer plate may then be translated and/or rotated toachieve the proper alignment to the mask arrangement. When the properorientation is achieved, the wafer plate is raised to be attached to thecarrier using, e.g., a series of magnets. In one embodiment, the waferplate includes suction holes, such that during the alignment process thevacuum is applied to the suction holes so as to hold and press the waferonto the wafer plate

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute apart of this specification, exemplify the embodiments of the presentinvention and, together with the description, serve to explain andillustrate principles of the invention. The drawings are intended toillustrate major features of the exemplary embodiments in a diagrammaticmanner. The drawings are not intended to depict every feature of actualembodiments nor relative dimensions of the depicted elements, and arenot drawn to scale.

FIG. 1 illustrates an embodiment of a multi-substrate processing system,wherein transport carriers support a line-array of substrates, butprocessing is performed on a two-dimensional array of substrates.

FIG. 1A illustrates an example of a system wherein the carriers remainin a horizontal orientation during transport and processing, while FIG.1B illustrates an example wherein the carriers are horizontal duringtransport and loading/unloading, but are vertical during processing.

FIG. 2 illustrates a multi-wafer carrier according to one embodiment,while FIG. 2A illustrates a partial cross-section.

FIG. 2B illustrates an example of carrier for processing silicon wafers,while FIG. 2C illustrates an example of a carrier for processing glasssubstrates.

FIG. 3A is a top view, while FIG. 3B is a side view of a load/unloadmechanism according to one embodiment. FIG. 3C illustrates an embodimentfor substrate alignment mechanism.

FIG. 4 illustrates an embodiment of a vacuum processing chamber 400 thatmay be used with the disclosed system.

FIG. 5 illustrates an embodiment for a mask and carrier assembly.

FIGS. 6A-6C illustrate three embodiments demonstrating how the vacuumchamber can be fitted with different processing sources of varying sizesand configurations.

FIGS. 7A-7E illustrate views of a multi-wafer carrier having anarrangement for dual-mask, according to various embodiments.

FIG. 8 is a cross section of an enlarged part of the frame, outer andinner masks, according to one embodiment, and FIG. 8A is a cross sectionof an enlarged part of the frame, outer and inner masks, according toanther embodiment.

FIG. 9 illustrates an embodiment of the outer mask, with the inner masknested therein.

FIG. 10 illustrates an embodiment of the inner mask for use in edgeisolation.

FIG. 11 illustrate an embodiment of the single wafer carrier.

FIG. 12 illustrate an embodiment of the outer mask, viewing from theunderside.

FIG. 13 illustrates an embodiment of a top frame to support the innerand outer masks.

FIG. 14 illustrates an embodiment of the inner mask for creatingplurality of holes in the wafer.

FIG. 15 illustrates an embodiment of the susceptor for use with the maskof FIG. 9.

FIGS. 16A-16D illustrate an embodiment wherein a wafer plate is attachedto a carrier from the underside, while the dual masks are attached fromthe topside.

FIG. 16E illustrates a double-mask arrangement according to oneembodiment.

FIG. 16F is a cross-section of part of the system according to oneembodiment, with an enlarge section illustrated in the callout.

FIG. 16G illustrates a wafer plate according to another embodiment,having vacuum mesas and peripheral cushion.

FIG. 16H illustrates the top part of the loading alignment stage,according to one embodiment.

FIG. 16I illustrates the top part of the unloading stage, according toone embodiment.

DETAILED DESCRIPTION

The following detailed description provides examples that highlightcertain features and aspects of the innovative processing system claimedherein. Various disclosed embodiments provide for a system whereinmultiple substrates, e.g., semiconductor or glass substrates, areprocessed simultaneously inside a vacuum processing chamber, such as,e.g., a plasma processing chamber. While glass substrates, such as thoseused for touchscreens are not generally considered wafers, it should beappreciated that references made to wafers in this disclosure are madefor convenience and ease of understanding, but that glass substrates maybe substituted for all such references.

FIG. 1 is a top-view illustration of an embodiment of a multi-substrateprocessing system, wherein transport carriers support a line-array ofsubstrates, but processing is performed on a two-dimensional array ofsubstrates. In the system 100 illustrated in FIG. 1, the substrates areloaded and unloaded at load/unload station 105, i.e., from the same sideof the system. However, it should be appreciated that the system mayalso be designed such that a loading station is provided on one side ofthe system, while an unloading station is provided on the opposite sideof the system. In some embodiments, loading and/or unloading ofsubstrates onto/from the carriers may be performed manually, while inothers automation is provided to perform one or both of these tasks.

The substrates are loaded onto carriers positioned in load/unloadstation 105, and which were transported from carrier return station 110.Each carrier supports a linear array of substrates, i.e., two or moresubstrates arranged in a single row, in a direction perpendicular to thedirection of travel inside the system. From load/unload station 105 thecarriers are moved via the carrier return station 110 to buffer station115. The carriers are parked in buffer station 115 until the low vacuumloadlock (LVLL) 120 is ready to accept them. In some embodiments, whichwill be described later, the buffer station also serves as the tiltingstation, wherein horizontally oriented carriers are tilted 90° to assumea vertical orientation. In such embodiments, clips are used to hold thesubstrate in place when assuming a vertical orientation.

At the proper time, valve 112 opens and the carriers positioned inbuffer station 115 are transported into LVLL 120. Valve 112 is thenclosed and the LVLL 120 is evacuated to a rough vacuum level. Thereaftervalve 113 opens and the carriers from LVLL 120 are transported into highvacuum loadlock (HVLL) 125. Once HVLL has been pumped to its vacuumlevel, valve 114 opens and the carriers from HVLL 125 are transportedinto processing chamber 130. The system may have any number ofprocessing chambers 130 aligned linearly such that the carriers may betransported from one chamber to the next via a valve positioned betweeneach two processing chambers. At the end of the last processing chamber,a valve is positioned that leads to the reverse loadlock arrangement asin the entrance to the system, i.e., first a HVLL and then a LVLL.Thereafter the carriers exit to the carrier return module 135 via valve116. From return module 135 the carriers are returned to carrier returnstation 110 using, e.g., conveyor positioned above or below theprocessing chambers 130 (not shown).

As noted above, each carrier supports a linear array of substrates,which makes it easier to load and unload the substrates, and makes thecarriers much easier to manufacture, handle, and transport. However, inorder to have high throughput of the system, each processing chamber 130is configured to house and simultaneously process a two-dimensionalarray of substrates positioned on several, i.e., two or more, carrierspositioned one after the other. For better efficiency, in the particularembodiment of FIG. 1, buffer station 115, LVLL 120 and HVLL 125 are eachconfigured to simultaneously house the same number of carrier as aresimultaneously housed inside the processing chamber 130. For example,each carrier may support three glass substrates in one row, but eachprocessing chamber is configured to process two carriers simultaneously,thus processing a two-dimensional array of 3×2 substrates.

According to other embodiments, the load locks and buffer chambers aresized to handle multiple carriers, e.g., two carriers, to provide forincreased pump/vent, and pressure stabilization times. Also, a bufferchamber can be used to transition carrier motion from one of station tostation motion to one of continues pass-by motion inside a processingchamber. For example, if one process chamber process carriers instationary mode while the next chamber processes in pass-by mode, abuffer chamber may be placed between these two chambers. The carriers inthe system create a continuous stream of carriers in the process chamberor module, and each process chamber/module may have 5-10 carrierscontinuously moving in a head to toe fashion past the process source(e.g., heat source, PVD, etch, etc).

As shown in FIG. 1, the parts of the system dedicated for transport,loading and unloading of substrates are positioned in atmosphericenvironment. On the other hand, all processing is performed in vacuumenvironment. Transport, loading and unloading in atmospheric environmentis much easier than in vacuum.

FIG. 1A illustrates an example of a system, such as that shown in FIG.1, wherein the carriers 200 remain in a horizontal orientation duringtransport and processing. The carriers are returned to the startingpoint via linear conveyor 140 positioned above the processing chambers.Linear conveyor 140 may be a conveyor belt or a series of motorizeswheels. As shown in FIG. 1A, each carrier 200 supports four substrates220 arranged linearly in one row. Also, for explanation purposes, thetop part of chamber 120 is removed, so as to expose the arrangement ofsix carriers positioned simultaneously therein. Therefore, according tothis embodiment, while each carrier supports four substrates, eachchamber process twenty-four substrates simultaneously.

FIG. 1B illustrates an example wherein the carriers are horizontalduring transport and loading/unloading, but are vertical duringprocessing. The arrangement of FIG. 1B is very similar to that of FIG.1A, except that the loadlock and processing chambers are flippedvertically, so as to process the substrates in a vertical orientation.The construction of loadlock and processing chambers in both embodimentsof FIGS. 1A and 1B may be identical, except that in FIG. 1A they aremounted horizontally, while in FIG. 1B they are mounted on their sidevertically. Consequently, the buffer stations 115 and the buffer station145 on the other end of the system, are modified to include a liftingarrangement which changes the orientation of the carriers 90°, as shownin buffer station 145.

FIG. 2 illustrates a line-array carrier according to one embodiment,which may be configured for processing silicon wafers, glass substrates,etc. As shown in FIG. 2, the construction of the line-array carrieraccording to this embodiment is rather simple and inexpensive. It shouldbe appreciated that the carrier can be configured for a different numberof substrates and substrate size, by simply mounting different chucks ontop of the carrier. Also, it should be appreciated that each processingchamber may be configured to accommodate several carrierssimultaneously, thus processing multiple wafers on multiple carrierssimultaneously.

The carrier 200 of FIG. 2 is constructed of a simple frame 205 which isformed by two transport rails 225 and two ceramic bars 210. The ceramicbar 210 improves thermal isolation of the susceptor (not shown) attachedthereto from the remaining parts of the chamber. At least one side ofeach ceramic bar 210 forms a fork arrangement 235 with the transportrail 225, as shown in the callout. A cavity 245 is formed in the forkarrangement 235, such that the ceramic bar 210 is allowed to freely move(illustrated by the double-head arrow) due to thermal expansion, and notimpart pressure on the transport rail 225.

A magnetic drive bar 240 is provided on each of the transport rails 225to enable transporting the carrier throughout the system. The magneticdrive bars ride on magnetized wheels to transport the carrier. Toenhance cleanliness of the system, the drive bars 240 may be nickelplated. This magnetic arrangement enables accurate transport withoutsliding of the carrier due to high accelerations. Also, this magneticarrangement enables large spacing of the wheels, such that the carrieris attached to the wheels by magnetic forces and may cantilever to alarge extent to traverse large gaps. Additionally, this magneticarrangement enables transport of the carrier in either vertical orhorizontal orientation, since the carrier is attached to the wheels bymagnetic forces.

Carrier contact assembly 250 is attached to the transport rail 225 andmates with a chamber contact assembly 252 (see callout) attached to thechamber. The chamber contact assembly has an insulating bar 260 having acontact brush 262 embedded therein. The contact assembly 250 has aconductive extension 251 (FIG. 2A) that is inserted between aninsulating spring 264 and insulting bar 260, thus being pressed againstbrush contact 262 so as to receive bias potential from the matingcontact. The bias may be used for, e.g., substrate bias, substratechucking (for electrostatic chuck), etc. The bias may be RF or DC(continuous or pulsed). The carrier contact assembly 250 may be providedon one or both sides of the carrier.

FIG. 2A is a partial cross-section showing how the carrier istransported and how it receives bias power. Specifically, FIG. 2Aillustrates the drive bar 240 riding on three magnetized wheels 267,which are attached to shaft 268. Shaft 268 extends beyond the chamberwall 269, such that it is rotated from outside the interior vacuumenvironment of the chamber. The shaft 268 is coupled to a motor viaflexible belt such as, e.g., an O-ring, to accommodate variations inshaft diameter.

FIG. 2B illustrates an example of carrier for processing silicon wafers,e.g., for fabricating solar cells. In FIG. 2B wafers 220 may be chuckedto susceptor 223 using, e.g., chucking potential. A lifter 215 may beused to lift and lower the wafers for loading and unloading. FIG. 2Cillustrates an embodiment wherein the carrier may be used for processingglass substrates such as, e.g., touchscreens. In this embodiment thesubstrates may be held in place using mechanical spring-loaded clamps orclips 227. The susceptor 224 may be a simple pallet with arrangement forthe spring-loaded clips.

FIGS. 3A and 3B illustrate an embodiment for substrate loading andunloading mechanism, in conjunction with the carrier return. FIG. 3A isa top view of the load/unload mechanism, while FIG. 3B is a side view.As shown in FIG. 1A, a conveyor returns the carriers after completion ofprocessing. The carriers are then lowered by elevator 107 andtransported horizontally to the loading/unloading station 105. As shownin FIGS. 3A and 3B, a dual conveyor, i.e., conveyors 301 and 303, areused to bring fresh substrates for processing and remove processedwafers. It is rather immaterial which one brings the fresh wafers andwhich one removes the processed wafers, as the system would work exactlythe same regardless. Also, in this embodiment it is shown that conveyors301 and 303 transport substrates in the opposite direction, but the sameresult can be achieved when both conveyors travel in the same direction.

The arrangement of FIGS. 3A and 3B supports handling two carrierssimultaneously. Specifically, in this embodiment processed substratesare unloaded from one carrier, while fresh substrates are loaded ontoanother carrier, simultaneously. Moreover, at the same time, processedsubstrates are deposited on the processed substrate conveyor and freshsubstrates are picked-up from the fresh substrates conveyor, to bedelivered to a carrier in the next round. This operation is performed asfollows.

The substrate pick-up mechanism is configured to have two motions:rotational and vertical motions. Four rows of chucks 307 are attached tothe substrate pick-up mechanism 305. The chucks 307 may be, for example,vacuum chucks, electrostatic chucks, etc. In this specific example, fourrows of Bernoulli chucks are used, i.e., chucks that can hold asubstrate using Bernoulli suction. The four rows of chucks arepositioned two on each side, such that when two rows of chucks arealigned with the carriers, the other two rows are aligned with theconveyors. Thus, when the pick-up mechanism 305 is in its loweredposition, one row of chucks picks up processed substrates from a carrierand another row deposits fresh substrates on another carrier, while onthe other side one row of chucks deposit processed substrates on oneconveyor and another row of chucks pick-up fresh substrate from theother conveyor. The pick-up mechanism 305 then assumes its elevatedposition and rotates 180 degrees, wherein at the same time the carriersmove one pitch, i.e., the carrier with the fresh substrates move onestep, the carrier from which processed substrates were removed movesinto a fresh substrate loading position, and another carrier withprocessed substrates moves into the unloading position. The pick-upmechanism 305 then assumes its lowered position and the process isrepeated.

To provide a concrete example, in the snapshot of FIG. 3A, carrier 311has processed substrates which are being picked-up by one row of chuckson pick-up arrangement 305. Carrier 313 is being loaded with freshsubstrates from another row of chucks of pick-up arrangement 305. On theother side of pick-up arrangement 305 one row of chucks is depositingprocessed substrates on conveyor 303, while another row of chucks ispicking up fresh substrates from conveyor 301. When these actions havebeen completed, pick-up arrangement 305 is raised to its elevatedposition and is rotated 180 degrees, as shown by the curved arrow. Atthe same time, all of the carriers move one step, i.e., carrier 316moves to the position previously occupied by carrier 317, carrier 313,now loaded with fresh substrates, moves to the spot previously occupiedby carrier 316, carrier 311, now empty, moves to the spot previouslyoccupied by carrier 313, and carrier 318, loaded with processedsubstrates moves into the spot previously occupied with carrier 311. Nowthe pick-up arrangement is lowered, such that carrier 311 is loaded withfresh substrates, processed substrates are removed from carrier 318, thesubstrates removed from carrier 311 are deposited onto conveyor 303, andfresh substrates are picked-up from conveyor 301. The pick-uparrangement 305 is then elevated, and the process repeats.

The embodiment of FIGS. 3A and 3B also utilizes an optional mask lifterarrangement 321. In this embodiment, masks are used to generate arequired pattern on the surface of the substrate, i.e., expose certainareas of the substrate for processing, while covering other areas toprevent processing. The carrier travels through the system with the maskplaced on top of the substrate until it reaches the mask lifer 321. Whena carrier with processed substrates reaches the mask lifter (in FIGS. 3Aand 3B, carrier 318), the mask lifter 321 assumes its elevated positionand lifts the mask from the carrier. The carrier can then proceed to theunload station to unload its processed substrates. At the same time, acarrier with fresh substrates (in FIG. 3B carrier 319), movers into themask lifter arrangement and mask lifter 321 assumes its lowered positionso as to place the mask onto the fresh substrates for processing.

As can be appreciated, in the embodiment of FIGS. 3A and 3B, the masklifter removes the masks from one carrier and places them on a differentcarrier. That is, the mask is not returned to the carrier from which itwas removed, but is rather placed on a different carrier. Depending onthe design and number of carriers in the system, it is possible thatafter several rounds a mask would be returned to the same carrier, butonly after being lifted from another carrier. The converse is also true,i.e., depending on the design and the number of carriers and masks inservice, it is possible that each mask would be used by all carriers inthe system. That is, each carrier in the system would be used with eachof the masks in the system, wherein at each cycle of processing throughthe system the carrier would use a different mask.

As shown in the callout, the carrier elevator may be implemented byhaving two vertical conveyor arrangements, one on each side of thecarriers. Each conveyor arrangement is made of one or more conveyor belt333, which is motivated by rollers 336. Lift pins 331 are attached tothe belt 333, such that as the belt 333 moves, the pins 331 engage thecarrier and move the carrier in the vertical direction (i.e., up ordown, depending on which side of the system the elevator is positionedat and whether the carrier return conveyor is positioned over or belowthe processing chambers).

FIG. 3C illustrates an embodiment for substrate alignment mechanism.According to this embodiment, chuck 345 has spring loaded alignment pins329 on one side and a notch 312 on the opposite side. A rotatingpush-pin 341 is configured to enter the notch 312 to push the substrate320 against the alignment pin 329 and then retract, as illustrated bythe dotted-line and rotational arrow. Notably, the rotating push-pin 341is not part of the chuck 345 or the carrier and does not travel withinthe system, but is stationary. Also, the spring-loaded alignment pin iscompressed to a lower position if a mask is used. Thus, a substratealignment mechanism is provided which comprises a chuck having a firstside configured with an alignment pin, a second side orthogonal to thefirst side and configured with two alignment pins, a third side oppositethe first side and configured with a first notch, and a fourth sideopposite the second side and configured with a second notch; thealignment mechanism further comprising a first push-pin configured toenter the first notch to push the substrate against the first alignmentpin, and a second push-pin configured to enter the second notch and pushthe substrate against the two alignment pins.

FIG. 4 illustrates an embodiment of a vacuum processing chamber 400 thatmay be used with the disclosed system. In the illustration of FIG. 4,the lid of the chamber is removed to expose its internal construction.The chamber 400 may be installed in a horizontal or verticalorientation, without any modifications to its constituents or itsconstruction. The chamber is constructed of a simple box frame withopenings 422 for vacuum pumping. An entry opening 412 is cut in onesidewall, while an exit opening 413 is cut in the opposite sidewall, toenable the carrier 424 to enter the chamber, traverse the entirechamber, and exit the chamber from the other side. Gate valves areprovided at each opening 412 and 413, although for clarity in theillustration of FIG. 4 only gate valve 414 is shown.

To enable efficient and accurate transport of the carrier 424 in ahorizontal and vertical orientation, magnetic wheels 402 are provided onthe opposing sidewall of the chamber. The carrier has magnetic bars thatride on the magnetic wheels 402. The shafts upon which the wheels 402are mounted extend outside the chamber into an atmospheric environment,wherein they are motivated by motor 401. Specifically, several motors401 are provided, each motivating several shafts using belts, e.g.,O-rings. Also, idler wheels 404 are provided to confine the carrierslaterally.

A feature of the embodiment of FIG. 4 is that the diameter of themagnetic wheels is smaller than the chamber's sidewall thickness. Thisenables placing magnetic wheels inside the inlet and outlet openings 412and 413, as shown by wheels 406 and 407. Placing wheels 406 and 407inside the inlet and outlet opening 412 and 413 enables smoothertransfer of the carriers into and out of the chamber, as it minimizesthe gap that the carriers have to traverse without support from wheels.

FIG. 5 illustrates an embodiment for a mask and carrier assembly.Progressing from left to right along the curved arrow, asingle-substrate mask assembly 501 is mounted onto a mask carrier 503,supporting several mask assemblies; and the mask carrier 503 is mountedonto a substrate carrier 505. In one embodiment, springs between thefloating mask assemblies 501 keep them in place for engagement withguide pins 507, provided on the substrate carriers 505, such that eachmask is aligned to its respective substrate. Each single-substrate maskassembly is constructed of an inner foil mask that is cheap and capableof many repeated uses. The foil mask is made of s flat sheet of magneticmaterial with perforations according to a desired design. An outer maskcovers and protects the inner mask by taking the heat load, so that thefoil mask does not distort. An aperture in the outer mask exposes thearea of the inner mask having the perforations. A frame holds the innerand outer masks onto the mask carrier 503. Magnets embedded in thesubstrate carrier 505 pull the inner foil mask into contact withsubstrate.

Each substrate support, e.g., mechanical or electrostatic chuck, 517supports a single substrate. The individual chucks 517 can be changed tosupport different types and/or sizes of substrates, such that the samesystem can be used to process different sizes and types of substrates.In this embodiment the chuck 517 has substrate alignment pins 519 whichare retractable, and provisions to align the substrate on top of thechuck. In this embodiment, the provisions to enable alignment consist ofa slit 512 accommodating a retractable pin that pushes the substrateagainst alignment pins 519 and then retracts out of the slit 512. Thisallows for aligning the substrate and the mask to the substrate carrier,such that the mask is aligned to the substrate.

As can be understood, the system described thus far is inexpensive tomanufacture and provide efficient vacuum processing of varioussubstrates, such as, e.g., solar cells, touchscreens, etc. The systemcan be configured with double or single end loading and unloading, i.e.,substrate loading and unloading from one side, or loading from one sideand unloading from the opposite side. No substrate handling is performedin vacuum. The system is modular, in that as many vacuum processingchambers as needed may be installed between the input and outputloadlocks. The vacuum chambers have a simple design with few parts invacuum. The vacuum chambers may be installed in a horizontal or verticalorientation. For example, for solar cell processing the system mayprocess the substrates in a horizontal orientation, while fortouchscreens the substrates may be processed in a vertical orientation.Regardless, loading, unloading and transport in atmospheric environmentis done with the substrates in a horizontal orientation. The processingsources, e.g., sputtering sources, may be installed above and/or belowthe substrates. The system is capable of pass-by or static processes,i.e., with the substrate stationary or moving during vacuum processing.The chambers may accommodate sputtering sources, heaters, implant beamsources, ion etch sources, etc.

For solar applications the vacuum chamber may include a low energyimplanter (e.g., less than 15 KV). For specific solar cell design, suchas PERC, IBC or SE, the mask arrangement may be used to perform maskedimplant. Also, texture etch may be performed with or without mask, usingan ion etch source or laser assisted etch. For point contact cells,masks with many holes aligned to the contacts can be used. Also, thickmetal layers can be formed by serially aligning several PVD chambers andforming layers one over the other serially.

For touch panel applications, the chambers may be used to deposit coldand/or hot ITO layers using PVD sources. The processing is performedwith several, e.g., three touch panels arranged widthwise on eachcarrier, and several, e.g., two, carriers positioned inside each chambersimultaneously for higher throughput but simpler handling. The samesystem can handle touchscreens for pads or cellphone size glass withoutany internal reconfigurations. Simply, the appropriate carrier isconfigured and the entire system remains the same. Again, no substratehandling is performed in vacuum.

The handling and processing operations can be the same for all types andsizes of substrates. An empty carrier moves to load from carrier returnelevator. If a mask is used, the mask is removed and stays at theelevator. Substrates are loaded onto the carrier in atmosphericenvironment. The carrier moves back to the elevator and the masks areplaced on top of the substrates. The carrier then moves into the loadlock. In vacuum the carrier transport is via simple magnetic wheelspositioned in chamber wall and energized from outside the chamber inatmospheric or vacuum environment. The chambers can have valves forisolation, and can have sources above or in a drawer for process belowthe substrates. The substrates can be removed at an unload end of thesystem, or left on carriers to return to the loading end, i.e., entryside of the system. Carriers return on simple conveyor belt from processend of the system to load end of the system. Simple pin conveyor liftsor lowers the carriers to or from load and unload stations.

FIGS. 6A-6C illustrate three embodiments demonstrating how the vacuumchamber can be fitted with different processing sources of varying sizesand configurations. In the examples of FIGS. 6A-6C it is assumed thatthe substrates are arrange three-wide, but of course more or lesssubstrates can be arranged on a carrier widthwise. Also, in FIGS. 6A-6Cit is assumed that the processing chamber can accommodate severalcarriers, e.g., two or three, for simultaneous processing. The sourcesillustrated in FIGS. 6A-6C may be any processing sources, such as, e.g.,PVD, etch, implant, etc.

FIG. 6A illustrates an embodiment wherein a single source 601 isprovided on chamber 600. This single source is used to process all ofthe substrates positioned inside the chamber 600. The source 601 mayhave length and/or width that covers all of the substratessimultaneously. For some sources, it may be too complicated or tooexpensive to fabricate a single source with such a large size. Forexample, if source 601 is a sputtering source, the target must be madevery large, which is expensive, complicated, and leads tounder-utilization. Therefore, according to the embodiments of FIGS. 6Band 6C several smaller sources are used. In the embodiment of FIG. 6Beach of the sources 603A-603C is wide enough to cover only a singlesubstrate, but it may cover more than one substrate lengthwise, i.e., inthe direction of substrate travel. By staggering the sources such thateach source covers only one of the substrate in each carrier, all of thesubstrates can be processed. Such an arrangement is particularlysuitable for pass-by processing. Conversely, in the embodiment of FIG.6C each of the sources 606A-606C is wide enough to cover all of thesubstrates in one carrier, i.e., in a direction perpendicular to thesubstrate travel direction, but is too narrow to cover all of thesubstrates positioned within the chamber. In fact, in some embodimentseach of the sources 606A-606C is even narrower than one substrate. Suchan arrangement is equally suitable for pass-by or static processing.

The embodiments described above provide for a vacuum processing chamberhaving a vacuum housing sized for housing and processing severalsubstrate carriers simultaneously. The housing is also configured forsupporting several processing sources simultaneously. The processingsources may be, e.g., sputtering sources, which may be narrow sourceshaving length sufficient to traverse all substrates held by a substratecarrier, but may be narrower than the width of a substrate positioned onthe carrier. Several such sources may be positioned back-to-back overthe entire or part of the length of the chamber in the travel directionof the carrier. The chamber has several shafts positioned on twoopposing sides to transport the carriers inside the chamber. Each shaftis rotated by a flexible belt that is motivated by a motor. Each shafthas several magnetic wheels positioned thereupon in alternating poleorder, i.e., while one wheel may have its outside circumferencemagnetized south and inside diameter magnetized north, the neighboringwheel would have its outer circumference magnetized north and insidediameter magnetized south. The chamber also has an entry sidewall havingan inlet opening and an exit sidewall opposite the entry sidewall andhaving an outlet opening; wherein a magnetized wheel arrangement ispositioned inside the entry sidewall and protruding into the inletopening and having a magnetized wheel arrangement positioned inside theexit sidewall and protruding into the outlet opening, so as to drive thesubstrate carriers passing through the inlet and outlet openings.

The disclosed system is a linear system wherein the chambers arearranged linearly, one chamber coupled to the next, such that substratecarriers enter the system from one side, traverse all the chambers in alinear fashion, and exit the system on the opposite side. The carriersmove from one chamber directly to the next via valve gates separatingthe chambers. Once a carrier exits the vacuum environment of the system,it enters an elevator and is moved vertically to a return conveyor,which transport the carrier horizontally back to the entry side of thesystem, wherein it enters another elevator and is moved vertically to beloaded with fresh substrates and enter the vacuum environment of thesystem again. While the carrier is transported in atmosphericenvironment it is held in a horizontal orientation. However, in oneembodiment, when the carrier enters the vacuum environment it is rotatedto a vertical orientation, such that the substrates are processed whileheld in a vertical orientation.

The system may have a loading and unloading station positioned at theentry side of the system. The loading and unloading system has arotating structure upon which four rows of chucks are positioned, tworows on each side of the rotation axis. On each side of the rotationaxis one row of chucks is configured for unloading processed substratesand one row of chucks is configured for loading fresh substrates. Therotating structure is configured for vertical motions, wherein when itassumes its lower position the structure picks-up substrates and when itassumes its elevated position the structure rotates 180 degrees. Also,when the structure is in its lowered position, on each side of therotation axis one row of chucks picks-up substrates while the other rowof chucks deposits, i.e., releases, its substrates. In one embodiment,two conveyors are provided across the entry to the system, wherein oneconveyor delivers fresh substrates while the other conveyor removesprocessed substrates. The rotating structure is configures such that inits lower position one row of chucks is aligned with the conveyordelivering fresh substrates while the other row of chucks is alignedwith the conveyor removing processed substrates. Simultaneously, on theother side of the rotation axis, one row of chucks is aligned with anempty carrier while the other row of chucks is aligned with a carrierholding processed substrates.

In some embodiments provisions are made to apply potential to thesubstrates. Specifically, each carrier includes a conductive strip that,when the carrier enters a processing chamber, is inserted into a slidingcontact comprising an elongated contact brush and a conformal insulatingspring that is configured to press the conductive strip against theelongated contact brush. An insulating strip, such as a Kapton strip,can be used to attach the conductive strip to the carrier.

When processing of the substrates requires the use of masks, the masksmay be placed individually on top of each substrate, or one mask may beformed to cover all substrates of one carrier simultaneously. The maskmay be held in place using, e.g., magnets. However, for accurateprocessing the mask must be made very thin, and consequently may deformdue to thermal stresses during processing. Additionally, a thin mask maycollect deposits rapidly and the deposits may interfere with theaccurate placing and masking of the mask. Therefore, it would beadvantageous to use the dual-mask arrangement according to theembodiments disclosed below.

FIGS. 7A-7E illustrate views of a multi-wafer carrier having anarrangement for dual-mask, according to various embodiments. FIG. 7Aillustrates a multi-wafer carrier with dual-masks arrangement, whereinthe mask arrangement is in the lower position such that the inner maskis in intimate physical contact with the wafer; FIG. 7B illustrates amulti-wafer carrier with dual-masks arrangement, wherein the maskarrangement is in the elevated position thereby enabling replacement ofthe wafers; FIG. 7C illustrates a multi-wafer carrier with dual-masksarrangement, wherein wafer lifters are included for loading/unloadingwafers; FIG. 7D illustrates a partial cross-section of a multi-wafercarrier with dual-masks arrangement, wherein the mask arrangement andthe wafer lifters are in the elevated position; and FIG. 7E illustratesa partial cross-section of a multi-wafer carrier with dual-masksarrangement, wherein the mask arrangement and the wafer lifter are inthe lower position.

Referring to FIG. 7A, the multi-wafer carrier, also referred to ascarrier support 700 has three separate single-wafer carriers orsusceptors 705, which are supported by a susceptor frame or bars 710,made of, e.g., ceramic. Each single-wafer carrier 705 is configured forholding a single wafer together with a dual-mask arrangement. In FIG. 7Athe dual-mask arrangement is in a lowered position, but no wafer issituated in any of the carriers, so as to expose the carriers'construction. In FIG. 7B the dual-mask arrangement is shown in thelifted position, again without wafers in any of the carriers. In theembodiments of FIGS. 7A-7E a lifter 715 is used to lift and lower thedual-mask arrangement; however, for lower cost and less complication,lifter 715 may be eliminated and the dual-mask arrangement may be liftedmanually. Transport rails 725 are provided on each side of the frames710, to enable transporting the carrier 700 throughout the system.

Each of single-wafer carriers 705 has a base 730 (visible in FIG. 7B),which has a raised frame 732 with a recess 735 to support a wafersuspended by its periphery. The base 730 with the frame 732 form apocket 740 below the suspended wafer, which is beneficial for capturingbroken wafer pieces. In some embodiments, the frame 732 is separablefrom the base 730. Outer mask 745 is configured to be mounted on theframe 732, so as to cover the frame 732 and cover the periphery of theinner mask, but expose the central part of the inner mask whichcorresponds to the wafer. This is exemplified by the cross-sectionillustration in the embodiment of FIG. 8.

In FIG. 8, base or susceptor 805 has raised frame 830 with recess 832,which supports wafer 820 at its periphery. The base 805 with frame 830forms pocket 840, and the wafer is suspended above the pocket. A seriesof magnets 834 are positioned inside the raised frame 830, so as tosurround the periphery of the wafer 820. In some embodiments, especiallyfor high temperature operations, the magnets 834 may be made of SamariumCobalt (SmCo). Inner mask 850 is positioned on top of the raised frame830 and the wafer 820, and is held in place by magnets 834, such that itphysically contacts the wafer. Outer mask 845 is placed over andphysically contacts the inner mask 850, such that it covers theperiphery of the inner mask 850, except for the area of the inner masksthat is designed for imparting the process to the wafer. An example ofouter mask 945 is shown in FIG. 9, in this example made of a foldedsheet of aluminum, wherein the inner mask is covered by the outer mask,except for a small peripheral edge 952, since the example is for an edgeshunt isolation processing. An example of the inner mask 750 for edgeshunt isolation is illustrated in FIG. 10, which is basically a flatsheet of metal having an aperture of size and shape as that of thewafer, except that it is slightly smaller, e.g., 1-2 mm smaller than thesize of the wafer. In the embodiment of FIG. 8, mask frame 836 isprovided to enable supporting and lifting of the inner and outer maskoff of the carrier. In such a configuration, the outer mask issandwiched between the mask frame 836 and the inner mask 850.

FIG. 8A illustrates another embodiment, which may be used, for example,for forming contact patterns on the back of a wafer. In this embodiment,the susceptor forms a top platform to support the wafer on its entiresurface. Magnets 834 are embedded over the entire area of the susceptorbelow the top surface of the susceptor. The inner mask 850 covers theentire surface of the wafer 820 and has plurality of holes according tothe contact design.

Turning back to FIGS. 7A-7E, lifter 715 can be used to raise the outermask, together with the inner mask. Also, wafer lifter 752 can be usedto lift the wafer off of the frame 730, so that it could be replacedwith a fresh wafer for processing, using a robot arm. However, lifters715 and 752 can be eliminated and the operations of lifting the masksand replacing the wafer may be done manually instead.

In the embodiments described above with reference to FIG. 8, the carriersupports the wafer on its peripheral edge, such that the wafer issuspended. The pocket formed below the wafer traps broken wafer piecesand prevents wraparound of deposited material. On the other hand, in theembodiment of FIG. 8A the wafer is supported over its entire surface.The mask assembly is lowered in place for sputter or other form ofprocessing, and is lifted, manually or mechanically, for loading andunloading of wafers. A series of magnets on the carrier help secure theinner mask in place and in tight contact with the wafer. After repeateduses, the outer and inner masks can be replaced, while the rest of thecarrier assembly can be reused. The frame 810, also referred to as maskassembly side bars, may be made from low thermal expansion material,such as Alumina or Titanium.

According to the above embodiments, the inner mask establishes anintimate gap free contact with the substrate. The outer mask protectsthe inner mask, the carrier and the frame from deposited material. Inthe embodiments illustrated, the outer and inner mask openings are in apseudo-square shape, suitable for applications to mono-crystalline solarcells during edge shunt isolation process. During other processes theinner mask has a certain apertures arrangement, while the outer mask hasthe pseudo-square shaped aperture. Pseudo-square shape is a square withits corners cut according to a circular ingot from which the wafer wascut. Of course, if poly-crystalline square wafers are used, the outerand inner mask openings would be square as well.

FIG. 11 illustrate an embodiment of the single wafer carrier 1105. Thewafer rests at its periphery on recess 1132. Magnets 1134, shown inbroken line, are provided inside the carrier all around the wafer.Alignment pins 1160 are used to align the outer mask to the carrier1105. An embodiment of the outer mask is shown in FIG. 12, viewing fromthe underside. The outer mask 1245 has alignment holes or recesses 1262corresponding to the alignment pins 1260 of the carrier 1205.

FIG. 13 illustrates an embodiment of a top frame 1336 used to hold theouter and inner masks and secure the masks to the susceptor. The topframe 1336 may be made by, e.g., two longitudinal bars 1362, heldtogether by two traverse bars 1364. The outer mask is held inside pocket1366. Alignment holes 1368 are provided to align the top frame to thesusceptor.

FIG. 14 illustrates an example of an inner mask with a hole-patterndesigned, for example, for fabricating plurality of contacts on thewafer. Such an inner mask can be used with the susceptor 1505 shown inFIG. 15, wherein the magnets 1534 are distributed over the entire areabelow the surface of the wafer. The magnets are oriented in alternatingpolarization.

An upper or outer mask may be made from thin, e.g., about 0.03″,aluminum, steel or other similar material, and is configured to matewith a substrate carrier. An inner mask is made from a very thin, e.g.,about 0.001 to 0.003″, flat steel sheet, or other magnetic materials,and is configured to be nested within the outer mask.

According to further embodiments, arrangement for supporting wafersduring processing is provided, comprising: a wafer carrier or susceptorhaving a raised frame, the raised frame having a recess for supporting awafer around periphery of the wafer and confining the wafer topredetermined position; an inner mask configured for placing on top ofthe raised frame, the inner mask having an aperture arrangementconfigured to mask part of the wafer and expose remaining part of thewafer; and an outer mask configured for placing over the raised frame ontop of the inner mask, the outer mask having a single opening configuredto partially cover the inner mask. A top frame carrier may be used tohold the inner and outer mask and affix the inner and outer masks to thewafer susceptor.

Magnets are located in the susceptor and alternate N—S—N—S—N completelyaround the frame or completely below the entire surface of the susceptorand directly under the wafer. The outer and inner masks are designed tobe held to the frame by magnetic forces only, so as to enable easy andfast loading and unloading of substrates.

The mask assembly is removable from the wafer carrier and support frameto load the substrate into the carrier. Both the outer and inner masksare lifted as part of the mask assembly. Once the wafer is located onthe carrier in the wafer pocket, the mask assembly is lowered back downonto the carrier. The inner mask overlaps the top surface of the wafer.The magnets in the carrier frame pull the inner mask down into intimatecontact with the substrate. This forms a tight compliant seal on theedge of the wafer. The outer mask is designed in order to preventdeposition on the thin compliant inner mask. As explained above, thedeposition process might cause the inner mask to heat, causing the maskto warp and loose contact with the wafer. If the mask loses contact withthe wafer the metal film will deposit in the exclusion zone on thesurface of the substrate wafer. The pocket and friction force created bythe magnets keep the substrate and mask from moving relative to eachother during transport and deposition, and the outer mask prevents filmdeposition on the inner mask and prevents the inner mask from warping.

The mask assembly can be periodically removed from the system with thecarrier by use of a vacuum carrier exchange. The carrier exchange is aportable vacuum enclosure with carrier transport mechanism. It allowsthe carriers to be exchanged “on the fly” without stopping thecontinuous operation of the system.

FIGS. 16A-16D illustrate an embodiment which may be implemented inside aloading station, such as, e.g., loading station 105. In this embodiment,a wafer plate is used to support the wafer, wherein the wafer plate isdetachably attached to the carrier from the underside, while the dualmasks are attached from the topside. FIGS. 16A-16D illustrate onlyrelevant parts of the system, so as to simplify the explanation. Also,some elements have been removed so as to enable visualization of thefeatures of the embodiment.

In FIGS. 16A-16D, the carrier 1600 comprises a simple frame 1603 havinga plurality of openings 1602 having a shape of the substrate, e.g.,semiconductor wafers, to be processed, but may be slightly larger toenable passage of the substrate therethrough. A plurality of waferplates 1610 are attached to the bottom of each carrier 1600. The waferplates 1610 are generally in a simple form of an aluminum plate and mayinclude attachment mechanism to attach the wafer plates to the undersideof the carrier 1600. When the wafer plate 1610 is attached to thecarrier 1600, the substrate 1620 positioned on the front surface of thewafer plate 1610 is aligned with and exposed through the opening 1602.The attachment mechanism may include mechanical clips, springs, magnets,etc. In the example illustrated a plurality of magnets 1612 (FIG. 16C)are used as the attachment mechanism.

A mask arrangement 1649 is positioned on the topside of each carrier1600, such that each mask arrangement 1649 covers one substrate exposedthrough the opening 1602. The mask arrangement 1649 may be a double-maskarrangement similar to that illustrated in FIGS. 9 and 10, but otherarrangements may be used, depending on the processing to be performed.For example, FIG. 16E illustrates a double-mask arrangement wherein theinner mask 1650 is a simple stamped flat metal sheet, which in thisexample is made of paramagnetic material. The outer mask 1645 is asimple aluminum plate having an opening similar in shape to the openingof the inner mask, but slightly larger. Note that in this dual-maskarrangement only the inner dimensions of the opening of the inner masksare critical, while all other dimensions do not require high fabricationtolerance, thus reducing the complexity and cost of fabricating themasks. Also, in this arrangement the masks are attached with a fixedorientation to the carrier 1600, such that the opening of the inner mask1650 is aligned with the opening 1602 in the carrier.

For clarity, the carrier 1600 is shown in some of the Figures as ifsuspended, but of course it is supported and is transported by atransport mechanism, such as, e.g., that illustrated in FIG. 1A. Thewafer plates, on the other hand, travel independently on a dedicatedconveyor belt 1632, until they are delivered to the alignment stage 1664and then attached to the carrier 1600. The operation of this mechanismis as follows. A lift mechanism 1662 is provided to load wafer plates1610 onto the wafer plate linear conveyor 1663, such as a conveyor belt.An alignment stage 1664 is provided for aligning each wafer plates 1610such that the wafer placed thereupon is aligned to the opening of theinner mask 1650 (using the camera 1670), and then raising the waferplate so that it attaches to the carrier 1600. In this embodiment, whenthe wafer plate is positioned on the alignment stage 1664, vacuum isapplied through holes 1614 in the wafer plate 1610, so as to hold thewafer and prevent it from moving during the alignment procedure. Oncethe wafer plate is attached to the carrier 1600, the vacuum may beterminated, since the clamping of the wafer plate to the carrierprevents the wafer from moving.

Additionally, a loading mechanism 1605 (FIG. 16D) may be employed forloading substrates onto the wafer plates 1610. Notably, the wafer plates1610 may be loaded with substrates prior to loading the wafer plates1610 onto the carriers. For example, in the instance of time illustratedin FIG. 16A, the sequence is shown wherein two wafer plates (identifiedas A and B) have no wafers, one wafer plate (identified as C) has waferplaced thereupon, but not yet attached to the carrier 1600, and onewafer plate (identified as D) has wafer placed thereupon and is raisedand attached to the carrier 1600.

The embodiment illustrated in FIGS. 16A-D is advantageous in that thetransport of the wafer plates for loading and unloading of wafers isdone separately from the transport of the carriers and masks. In thismanner, the wafer plates can be removed from the system for cleaning.Also, since the wafer plates are made of rather inexpensive aluminumslabs, they can be easily exchanged with new ones, without affecting theoperation of the system.

As illustrated more clearly in FIGS. 16B and 16D, empty carriers 1600are delivered to the working station by elevator 1635 and are thenpositioned onto a conveyor, e.g., a conveyor belt 1633. In this exampleeach carrier is configured to accommodate two wafer plates forprocessing two wafers simultaneously, but the carrier can be made toaccommodate other number of wafer plates. Another conveyor, e.g.,conveyor belt 1632 transports wafer plates 1610 under conveyor 1633. Awafer loading mechanism, e.g., robot 1605 places wafers onto the waferplates 1610. When a wafer is placed onto a wafer plate 1610, theconveyor 1632 moves the wafer plate 1610 to the alignment station, abovealignment stage 1664. Vacuum pump 1647 is then used to deliver suctionpower to the wafer plate so as to hold the wafer onto the wafer plateand the wafer plate onto the alignment stage. Specifically, the waferplate has vacuum holes 1614 below the wafer. When suction is appliedthrough these holes 1614 the wafer is held onto the wafer plate andseals these holes. Consequently, the same suction, blocked by the wafer,causes the wafer plate to be held against the alignment stage viavacuum. Meanwhile, conveyor 1633 delivers an empty carrier 1600 to thealignment station, right above the stage 1664. The carrier in thealignment station has a mask arrangement 1649 attached thereto over theopening 1602. To perform the alignment, actuators 1661 raise the carrier1600 off the conveyor, so that it is held mechanically in a staticposition. Stage 1664 then lifts the wafer plate and performs rotation ortranslation as necessary to align the wafer to the opening of the mask1645, as determined from the controller 1671 using the images obtainedby camera 1670. Once the proper alignment is achieved, the stage furtherraises the wafer plate until the wafer plate contacts the underside ofthe carrier. At this point the vacuum is terminated, such that the waferplate is attached to the carrier via mechanical or magnetic means. Thestage 1664 then lowers to accept another wafer plate, while the conveyor1633 moves the loaded carrier out of the alignment station and brings anunloaded carrier to repeat the process.

In one embodiment a method for loading and processing substratesproceeds as follows: carriers without wafers return from unloadingstation. In embodiments wherein the wafer plates were delivered by beingattached to the carriers, the wafer plates are removed from the carriersand lowered to conveyor, e.g., by lift mechanism 1662. Alternatively,the wafer plates 1610 may be delivered independently of the carriers. Aloading mechanism places a plurality of wafers onto corresponding waferplates, one wafer per each wafer plate. Then the wafer plates andcarrier are moved independently to an alignment station, wherein acamera 1670 images the wafer and the mask. The images are provided tothe controller 1671 that checks the alignment of the mask opening withrespect to the wafer. That is, in this particular example, the mask 1645is attached to the carrier in a fixed orientation. The wafer carrier ispositioned on an (x-y-z-theta) alignment stage 1664 positioned below thecamera. The wafer's position/orientation with respect to the maskopening is calculated by the controller using the images provided by thecamera 1670, and the controller 1671 sends signals to the stage 1664 tocorrect the orientation if necessary by translating or rotating thex-y-z-theta stage 1664. The wafer plate is then lifted by the stage andis attached to the carrier, wherein the wafer is positioned into contactwith the inner mask. In this position magnetic force holds the waferplate into carrier such that the wafer cannot move, and the vacuum maythen be released. Also, the same magnetic force holds the dual-maskarrangement pressed against the wafer. Consequently the wafer isprevented from moving from its aligned position. That is, in oneembodiment, when the wafer plate is in the alignment station and thewafer has been positioned in alignment position, a vacuum is applied tothe wafer via the wafer plate, such that the wafer is prevented frommoving. However, once the wafer plate is attached to the carrier and themask contacts the wafer, the vacuum pumping may be terminated. Next thecarriers are moved throughout the system for processing and whenprocessing is completed the sequence repeats.

In one embodiment, after processing is completed the wafers are removedfrom the wafer plates in an unload station and then the wafer plates aretilted into a vertical orientation. This ensures that if any wafer wasbroken during processing the fragments are dumped prior to returning thewafer plate for further processing.

FIG. 16F is a cross-section of part of the system, with an enlargesection illustrated in the callout. It can be seen that in thisembodiment a dual mask arrangement is used, wherein the inner mask 1650is covered by the outer mask 1645. Magnets 1612 are provided around theperiphery of the wafer plate 1610 to hold the wafer plate 1610 to theunderside of the carrier 1605.

In a specific embodiment, the following sequence is executed, whereineach of the carriers is capable of supporting five wafer plates. Fivewafers are loaded onto five individual wafer plates. The five loadedwafer plates then move to the alignment station. In this specificembodiment, each of the wafer plates has a gasket with magnets aroundthe edge. The gasket may be made of fluoroelastomers that arecategorized under the ASTM D1418 and ISO 1629 designation of FKM. In thealignment station the five wafer plates are lifted off conveyor by thealignment stage (here, five separate alignment stages are provided so asto simultaneously align five wafer plates.). When the wafer plates arelifted off the conveyor, vacuum holds the wafer plate securely on liftsand the wafers securely on the wafer plates. At this point, the fivewafers are imaged individually by five cameras. Then the conveyor movesthe carrier into the alignment station, just above the wafer plates, sothat each opening in the carrier is above one of the wafer plates. Thecarrier is then lifted off the conveyor belt, so as to position thecarrier in a mechanically secured static position. The cameras are thenactivated to image the five openings on the carrier. The system thencalculates the x-axis and y-axis of each mask opening and the x-axis andy-axis of each of the five wafers. The five X/Y/Theta stages then moveeach wafer to align the x-axis and y-axis of each wafer to coincide withthe x-axis and y-axis of each corresponding mask. The five wafer platesare then lifted up until the wafer plates contact and attach to thecarrier, such that the wafer on each of the wafer plates is positionedwithin the corresponding opening in the carrier and contacts thecorresponding inner mask. The vacuum is then released, such that thewafer plates are now attached mechanically or magnetically to carrier.The carrier and stages are then lowered and the sequence repeats for thesecond row.

FIG. 16G illustrate an alternative embodiment of the wafer plate 1610.In this embodiment, the wafer plate 1610 is still made of an aluminumslab. Three vacuum mesas 1613 are provided on the front surface of thewafer plate 1610, each mesa having a vacuum hole 1614. In oneembodiment, the mesas are made of soft material and each mesa includes aseal 1611 around each hole 1614. Thus, when a wafer is placed on top ofthe wafer plate 1610 and vacuum is applied to the mesas, the wafer isheld by vacuum on top of the three mesas, such that the wafer does notcontact the surface of the wafer plate 1610. Since only three mesas areprovided, no forces are applied against the wafer to cause it to bend orbreak. Also, a cushioning ring 1618 is provided around the periphery ofthe wafer plate 1610. The magnets 1612 are embedded in the cushioningring 1618. In this embodiment, the cushioning ring does not providehermetic seal to the wafer, to avoid sucking the wafer towards thesurface of the wafer plate 1610. This is achieved by, e.g., making thecushioning ring 1618 out of porous material or providing air channels1619 providing fluid communication from the ambient to the space betweenthe wafer and the top surface of the wafer plate 1610.

FIG. 16H illustrates the top surface of a seat plate 1672 that can befitted to either the loading stage 1669 or the alignment stage 1664, orto both, according to one embodiment. The seat plate 1672 is affixed tothe top of the loading stage 1669 and the alignment stage 1664, and thewafer plate 1610 is seated upon the seat plate 1672. As shown in FIG.16H, two sets of vacuum holes are provided through the top surface ofthe seat plate 1672: the holes of the first set 1668 are aligned withand deliver vacuum passage to the corresponding vacuum holes 1614 of thewafer plate 1610, so as to deliver suction to the wafer to hold thewafer to the wafer plate 1610. The holes of the second set, 1667,provide suction force to hold the wafer plate 1610 to the seat of thealignment stage 1664. Thus, in one embodiment, when a carrier isdelivered to the loading station, the loading stages are raised and thesuction is activated at least to holes 1667 of the second set, such thateach of the loading stages attaches a corresponding wafer plate byvacuum force. When the loading stages are lowered, the wafer plates 1610are separated from the carrier by the vacuum force that holds the waferplates to the seat plate 1672. Since in one embodiment the carriersreturn without the wafers (the wafers being unloaded at the unloadingstation, during this process no vacuum needs to be delivered to holes1668. Indeed, these holes may be plugged, or the loading stages providedwith seat plates 1672 having only vacuum holes 1667.

FIG. 16I illustrates the top surface view of a seat plate 1674 that canbe fitted to the unloading stage, e.g., at carrier return chamber 135shown in FIGS. 1, 1A and 1B. The seat plate 1674 is affixed to the topof the unloading stage, and the wafer plate 1610 is seated upon the seatplate 1674. As shown in FIG. 16I, the holes of the first set 1668 areeither blocked or not provided, such that there is no vacuum passage tothe corresponding vacuum holes 1614 of the wafer plate 1610. That is, inthe unloading stage no suction is applied to the wafer to hold the waferto the wafer plate 1610. The holes of the second set, 1667, providesuction force to hold the wafer plate 1610 to the seat of the alignmentstage 1664. Thus, in one embodiment, when a carrier is delivered to theunloading station, suction is activated to holes 1667 to hold thecorresponding wafer plate by vacuum force. Then, the unloading stagetilts the seat plate 1674, as illustrated by the curved arrow, such thatif there are any pieces of a broken wafer on the wafer plate 1610, thepieces would slide off the wafer plate 1610 and into a collection trough1682.

As can be understood from the above disclosure, a system for processingwafers is provided, comprising: a loading station having a loading stagemovable in vertical direction and having loading seat plate, the loadingseat plate having a first set of suction holes; an alignment stationhaving an alignment stage movable in x-y-z and rotation directions andhaving alignment seat plate, the alignment seat plate having a secondset of suction holes and a third set of suction holes; an unloadingstation having an unloading stage movable in vertical and tiltdirections, and having an unloading seat plate, the unloading seat platehaving a fourth set of suction holes, the unloading seat plate assuminga vertical orientation when the unloading stage moves in the tiltdirection; at least one vacuum processing chamber situated between thealignment station and the unloading station; a plurality of waferplates, each wafer plate configured for supporting one wafer and havinga fifth set of suction holes configured to apply vacuum to a waferpositioned on the wafer plate; a transport mechanism configured tocontinuously transport the plurality of wafer plates from the loadingstation, to the alignment station, to the vacuum processing chamber, tothe unloading station, and back to the loading station; wherein thefirst set, the second set, and the fourth set of suction holes areconfigured to apply vacuum to the wafer plate, and the third set ofvacuum holes are aligned with and provide fluid communication to thefifth set of suction holes. The system may further comprise a pluralityof carriers, each carrier configured to support a plurality of waferplates from an underside of the carrier, and a plurality of masks, eachmask attached over a top surface one of the carriers.

Each wafer plate may comprise three mesas, each mesa accommodating oneof the suction holes. Each mesa may further comprise a seal around thesuction hole. Each wafer plate may further comprise a cushion ring and aplurality of magnets attached to the cushion ring. The system mayinclude a bin configured to accept wafer segments from a wafer platewhen the unload station moves in the tilt direction. The alignmentstation may further comprise a camera aligned to image a waferpositioned on a wafer plate seated on the alignment stage and to image amask attached to a carrier. Also, a controller receives images from thecamera and sends alignment signals to the alignment stage so as to alignthe wafer to the mask. The transport mechanism may comprise a firstconveyor belt configured to transport the carriers and a second conveyorbelt configured to transport the wafer plates.

While this invention has been discussed in terms of exemplaryembodiments of specific materials, and specific steps, it should beunderstood by those skilled in the art that variations of these specificexamples may be made and/or used and that such structures and methodswill follow from the understanding imparted by the practices describedand illustrated as well as the discussions of operations as tofacilitate modifications that may be made without departing from thescope of the invention defined by the appended claims.

The invention claimed is:
 1. A system for processing wafers in aplurality of vacuum processing chambers, comprising: a plurality ofcarriers, each of the plurality of carriers comprising a frame having aplurality of openings, each of the plurality of openings configured toaccommodate one wafer; a transport mechanism, the plurality of carriersmoved by the transport mechanism throughout the system and from oneprocessing chamber to the next; a plurality of wafer plates, each of theplurality of wafer plates configured for supporting one wafer; anattachment mechanism attaching at least two of the plurality of waferplates to each of the plurality of carriers, wherein each wafer plate ofthe plurality of wafer plates is attached to a position at an undersideof a corresponding carrier of the plurality of carriers, such that eachof the wafer plates is positioned below a corresponding opening of theplurality of openings; a plurality of masks, each mask of the pluralityof masks attached to a corresponding carrier of the plurality ofcarriers over a front side of one of the plurality of openings; analignment stage, configured for supporting one of the plurality of waferplates under one of the plurality of openings of one of the plurality ofcarriers, the alignment stage movable in translation, rotation, andelevation; a camera positioned to image one of the plurality of masksand to image a wafer supported on one of the wafer plates whilepositioned on the alignment stage; and, a controller configured forreceiving images from the camera and sending correction signals to thealignment stage.
 2. The system of claim 1, wherein said plurality ofmasks comprise: a plurality of inner masks, each of the plurality ofinner masks configured for placing on top of one of the plurality ofcarriers in alignment with one of the plurality of openings, the innermask having an opening-pattern, a plurality of outer masks, each of theplurality of outer masks configured for placing on top of acorresponding inner mask of the plurality of inner masks, the outer maskhaving an opening configured to partially cover the corresponding innermask.
 3. The system of claim 1, wherein each of the plurality of waferplates comprises a flat plate made of aluminum.
 4. The system of claim3, wherein the attachment mechanism comprises a plurality of magnetsattached to each of the plurality of wafer plates.
 5. The system ofclaim 4, wherein each of the plurality of wafer plates further comprisesvacuum holes.
 6. The system of claim 5, wherein the alignment stagecomprises a seat plate, the seat plate having a first set of vacuumholes aligned to the vacuum holes of each of the plurality of waferplates and a second set of vacuum holes configured to deliver suction tohold one of the plurality of wafer plates to the seat plate.
 7. Thesystem of claim 5, further comprising an unloading stage comprising anunloading seat plate, the unloading seat plate configured to block thevacuum holes of one of the plurality of wafer plates positioned at theunloading stage to thereby prevent fluid communication to the vacuumholes, the unloading seat plate comprising a set of vacuum holesconfigured to deliver suction to hold one of the plurality of waferplates to the unloading seat plate.
 8. The system of claim 5, whereineach of the plurality of wafer plates comprises three mesas, each mesaaccommodating one of the vacuum holes.
 9. The system of claim 8, whereineach mesa further comprises a seal around the suction hole.
 10. Thesystem of claim 9, wherein each of the plurality of wafer plates furthercomprises a cushion ring and a plurality of magnets attached to thecushion ring.
 11. The system of claim 1, further comprising a conveyorbelt configured for transporting the wafer plates to a position insidethe field of view of the camera.
 12. The system of claim 1, wherein thetransport mechanism comprises a first linear conveyor configured totransport the plurality of carriers and a second linear conveyorconfigured to transport the plurality of wafer plates when the waferplates are detached from the carriers.
 13. The system of claim 1,further comprising a substrate unload station having a mechanism fortilting one of the plurality of wafer plates into a vertical orientationover a collection bin for collecting any wafer fragments.
 14. The systemof claim 1, further comprising: a loading station having a loading stagemovable in vertical direction and having loading seat plate, the loadingseat plate having a first set of suction holes; the alignment stagehaving an alignment seat plate, the alignment seat plate having a secondset of suction holes and a third set of suction holes; an unloadingstation having an unloading stage movable in vertical direction, andhaving an unloading seat plate, the unloading seat plate having a fourthset of suction holes; and, wherein the transport mechanism continuouslytransports each of the plurality of wafer plates from the loadingstation, to the alignment station, to the vacuum processing chambers, tothe unloading station, and back to the loading station.
 15. The systemof claim 14, wherein the unloading stage is further movable in tiltdirections, the unloading seat plate assuming a vertical orientationwhen the unloading stage moves in the tilt direction.
 16. The system ofclaim 14, further comprising a bin configured to accept wafer fragmentsfrom one of the plurality of wafer plates when the unload station movesin the tilt direction.
 17. The system of claim 1, wherein the attachmentmechanism includes a plurality of magnets.
 18. The system of claim 1,wherein the transport mechanism comprises a first conveyor beltconfigured to transport the plurality of carriers and a second conveyorbelt configured to transport the plurality of wafer plates.
 19. A systemfor processing wafers in a plurality of vacuum processing chambers,comprising: a plurality of carriers, each of the plurality of carrierscomprising a plurality of openings, each of the plurality of openingssized to accommodate one wafer; a transport mechanism transporting theplurality of carriers throughout the system and from one processingchamber to the next; a plurality of wafer plates, each of the pluralityof wafer plates sized for supporting one wafer; an attachment mechanismattaching at least two of the plurality of wafer plates to each of theplurality of carriers, wherein each of the plurality of wafer plates isattached to a corresponding position at an underside of a correspondingcarrier of the plurality of carriers, such that a wafer positioned onone of the plurality of wafer plates is situated within one of theplurality of openings in one of the plurality of carriers; a pluralityof masks, each of the plurality of masks attached over a front side ofone of the plurality of openings; an alignment stage, configured forsupporting one of the plurality of wafer plates under one of theplurality of openings, the alignment stage movable in translation,rotation, and elevation; a camera positioned to image one of theplurality of masks and to image a wafer positioned on one of theplurality of wafer plates while positioned on the alignment stage; and,a controller configured for receiving images from the camera and sendingcorrection signals to the alignment stage.
 20. The system of claim 19,wherein the alignment stage comprises an alignment seat plate, thealignment seat plate having a set of suction holes.
 21. The system ofclaim 20, wherein each of the plurality of masks comprises an inner maskand an outer mask.
 22. The system of claim 19, wherein the attachmentmechanism comprises a plurality of magnets.
 23. The system of claim 19,wherein each of the plurality of carriers further comprises a pluralityof magnets positioned to attach corresponding masks of the plurality ofmasks to each corresponding carrier of the plurality of carriers.
 24. Asystem for processing wafers, comprising: a loading station; anunloading station; a plurality of vacuum processing chambers; aplurality of carriers, each carrier of the plurality of carrierscomprising a plurality of openings, each opening of the plurality ofopenings sized to accommodate one wafer; a transport mechanismtransporting the plurality of carriers through the plurality of vacuumprocessing chambers; a plurality of wafer plates, each of the pluralityof wafer plates sized for supporting one wafer; an attachment mechanismattaching a number of the plurality of wafer plates to each of theplurality of carriers, wherein each of the plurality of wafer plates isattached to a corresponding position at an underside of a correspondingcarrier of the plurality of carriers, such that each of the plurality ofwafer plates is situated within one of the plurality of openings; aplurality of masks, each mask of the plurality of masks attached over afront side of one of the plurality of opening; an alignment stage,supporting one of the plurality of wafer plates under one of theplurality of openings, the alignment stage movable in translation,rotation, and elevation; a camera positioned to image one of theplurality of masks and to image a wafer positioned on one of theplurality of wafer plates while positioned on the alignment stage; and,a controller configured for receiving images from the camera and sendingcorrection signals to the alignment stage.
 25. The system of claim 24,wherein: the loading station comprises a loading stage movable invertical direction and having loading seat plate; the alignment stagehaving alignment seat plate; and the unloading station comprises anunloading stage movable in vertical direction.
 26. The system of claim25, wherein the loading seat plate comprises a set of suction holes. 27.The system of claim 25, wherein the alignment seat plate comprises a setof suction holes.
 28. The system of claim 25, wherein the unloadingstage is further movable in tilt directions, the unloading seat plateassuming a vertical orientation when the unloading stage moves in thetilt direction.